We studied the responses of 12 beetle families to long-rotation (extending the rotation period) and related ecological variables on the biodiversity of beetle families in larch (Larix kaempferi) plantations. Aerial Malaise traps were deployed in the forest understory and the canopy in the plantations to catch beetles. The diversity of twelve beetle families (Cerambycidae, Elateridae, Chrysomelidae, Curculionidae, Melandryidae, Lycidae, Erotylidae, Scarabaeidae, Cantharidae, Coccinellidae, Staphylinidae, and Scolytidae) in the understory & the canopy of long-rotation and middle-aged plantations was compared. The relationships between the species richness of each beetle family and ecological variables were also identified. We found that diversity of each beetle family was differently influenced by ecological variables, that some of these variables changed in quality and quantity by long rotation, and that beetle diversity tended to increase with long-rotation, especially in the canopy. We discuss on the basis of these findings the ways to improve biodiversity in plantations.